It is known to use a conventional drill press to drill finger and thumb holes in bowling balls. A problem with a drill press is that the drill bit spindle is incapable of holding the drill bit in a true position on a drill line. Also, it is necessary to provide the drill press with a specially constructed support for both holding the bowling ball and moving it in position relative to the drill line. By way of example, U.S. Pat. No. 2,973,674, granted Mar. 7, 1961, to Joseph A. Hladik, discloses a ball holding and positioning fixture which includes three snubbers atop three standards, adapted for clamping a bowling ball between them. The snubbers are constructed from a resilient material and thus will permit some movement of the bowling ball. Also, there is some give in the clamp screw which moves one of the snubbers relative to the other two snubbers.
A principal object of the present invention is to form the finger and thumb openings by use of a standard vertical axis milling machine. A milling machine possesses a spindle constructed to hold the milling bit of the hole boring bit type true on a vertical drill line. A milling machine also includes a built in mechanism for positioning the support table in any horizontal position relative to the milling bit axis. A further object of the invention is to provide a vacuum holder for the bowling ball which is constructed to hold the bowling ball in an unyielding position on the support table.
The aforementioned U.S. Pat. No. 2,973,674, and the following additional U.S. patents, should be considered for the purpose of putting the present invention into proper perspective relative to the prior art: U.S. Pat. No. 2,269,946, granted Jan. 13, 1942, to Joseph A. Lange; U.S. Pat. No. 2,283,469, granted May 19, 1942, to Henry B. Shepard; U.S. Pat. No. 2,428,669, granted Oct. 7, 1947, to Henry Hopkins; U.S. Pat. No. 2,490,120, granted Dec. 6, 1949, to Clifford L. Ellison and Louis Pospischek; U.S. Pat. No. 2,879,679, granted Mar. 31, 1959, to Wilber L. Neff; U.S. Pat. No. 3,095,767, granted Jul. 2, 1963, to Alexander Jesonis; U.S. Pat. No. 3,143,901, granted Aug. 11, 1964, to Charles E. Bawtinheimer; U.S. Pat. No. 3,179,013, granted Apr. 20, 1965, to Bernard Goldsmith; U.S. Pat. No. 3,262,340, granted Jul. 26, 1966, to Martin V. Sammons, Robert D. Baker and John F. Nixon; U.S. Pat. No. 3,329,043, granted Jul. 4, 1967, to Robert M. Stanford; U.S. Pat. No. 3,349,647, granted Oct. 31, 1967, to Louis J. Stan; U.S. Pat. No. 3,382,740, granted May 14, 1968, to Russell P. Lotta; U.S. Pat. No. 3,415,146, granted Dec. 10, 1968, to Kenneth K. Schroeder, Jr.; U.S. Pat. No. 3,465,619, granted Sep. 9, 1969, to David P. Blaker and Kenneth J. Conrad; U.S. Pat. No. 3,521,506, granted Jul. 21, 1970, to Frank Di Nardo; U.S. Pat. No. 3,714,703, granted Feb. 6, 1973, to Travis N. Maples; U.S. Pat. No. 3,689,165, granted Sep. 5, 1972, to Edward E. Small; and U.S. Pat. No. 3,843,276, granted Oct. 22, 1974, to Michael Williams.
A cursory examination of these patents will show that the ball holding fixtures disclosed by the patents are complicated and because of the complexity are slow to use. Also, they include mechanical clamp members which are to some extent yieldable. U.S. Pat. No. 3,714,703 discloses a type of vacuum holder for holding a bowling ball while drilling finger holes. However, an elastomeric seal ring is provided at the rim of the vacuum holder and the bowling ball is seated on this elastomeric seal ring. Also, the vacuum holder is at the upper end of an elongated rotary shaft which is to some extent yieldable. This arrangement of the seal ring, and the mounting of the vacuum holder for rotation, are both undesirable if the vacuum holder is to be expected to hold the bowling ball rigid while holes are being drilled in the ball. An object of the present invention is to provide a vacuum holder which is constructed and arranged to hold a bowling ball very rigid, permitting both accurate placement and true formation of the finger and thumb holes by use of a milling machine. A further object of the invention is to provide a technique of using a standard vertical axis milling machine and the vacuum holder together for enabling a relatively unskilled operator to quickly, easily and accurately form finger and thumb holes in bowling balls, including oblong holes.